With network product upgrading, a size and power consumption of a module used in a network are continuously decreasing, to meet requirements of continuous cost reduction and performance improvement. Because of its unique characteristics such as low costs, a subminiature size, and low power consumption, a silicon-based photonic component has attracted wide attention in the industry in recent years, and has become one of key trends under consideration for network product upgrading.
A flare size (0.3 um) of a silicon optical waveguide is far less than a mode size (9 um) of a fiber core of an optical fiber. Therefore, a coupling loss is relatively large because of a mismatch between sizes of optical coupling mode fields of the silicon photonic waveguide and the fiber core of the optical fiber. Currently, silicon-optical coupling solutions mainly include the following: One coupling solution is vertical coupling by using a grating coupler (grating coupler). In this solution, mode fields match. However, a loss of the grating coupler is relatively large, and the grating coupler is polarization-sensitive and wavelength-sensitive. Therefore, usage of this coupling solution is restricted. Another coupling solution is end face coupling. In this solution, a conical waveguide is used to implement flare size expansion. This structure has a high requirement on a technique of processing a cone tip structure. In addition, a flare size expansion effect is limited, and a flare size cannot match a mode size of an optical fiber.